Overview
Chronic visceral acid sphingomyelinase deficiency (ASMD) — also known as Niemann-Pick disease type B, or non-neuronopathic Niemann-Pick disease — is a rare inherited condition caused by a shortage of an enzyme called acid sphingomyelinase. This enzyme normally breaks down a fatty substance called sphingomyelin inside cells. When it does not work properly, sphingomyelin builds up in organs throughout the body, especially the liver, spleen, and lungs. Unlike the more severe type A form, type B (chronic visceral ASMD) mainly affects the organs rather than the brain and nervous system, though some patients do experience mild neurological involvement. The most noticeable effects are an enlarged spleen and liver, which can cause abdominal discomfort and a swollen belly. Lung involvement is also common and can lead to breathing difficulties, reduced exercise tolerance, and frequent respiratory infections. Many patients also have abnormal cholesterol and lipid levels in the blood, which raises the risk of heart disease over time. Low blood cell counts due to an overactive spleen can cause fatigue, easy bruising, and increased risk of infections. For many years, treatment was only supportive — managing symptoms rather than the underlying cause. However, olipudase alfa (brand name Xenpozyme), an enzyme replacement therapy, was approved by the FDA in 2022 and represents a major advance. It directly replaces the missing enzyme and has been shown to reduce organ enlargement and improve lung function. With proper management, many people with chronic visceral ASMD can live into adulthood, though ongoing monitoring and specialist care are essential.
Also known as:
Key symptoms:
Enlarged spleen (splenomegaly) causing a swollen or uncomfortable bellyEnlarged liver (hepatomegaly)Breathing difficulties and reduced ability to exerciseFrequent lung infections or pneumoniaLow red blood cell count (anemia) causing tiredness and pale skinLow platelet count leading to easy bruising or bleedingLow white blood cell count increasing infection riskAbnormal cholesterol and blood fat levelsDelayed growth or short stature in childrenMild neurological symptoms in some patients (such as balance problems)Cherry-red spot in the eye (less common in type B than type A)Bone pain or reduced bone densityFatigue and low energy
Clinical phenotype terms (47)— hover any for plain English
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Variable
Can begin at different ages, from infancy through adulthood
Treatments
No FDA-approved treatments are currently listed for Chronic visceral acid sphingomyelinase deficiency.
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Rare Disease Specialist
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Chronic visceral acid sphingomyelinase deficiency.
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Questions for your doctor
Bring these to your next appointment
- Q1.Am I a candidate for olipudase alfa (Xenpozyme) enzyme replacement therapy, and what would the treatment schedule look like?,How severely are my liver, spleen, and lungs affected right now, and how will we track changes over time?,Should my family members be tested to see if they are carriers or affected?,What activities or sports should I or my child avoid because of the enlarged spleen?,Are there any clinical trials I should know about for new treatments?,What signs or symptoms should prompt me to go to the emergency room?,How will this condition affect growth and development in my child long-term?
Common questions about Chronic visceral acid sphingomyelinase deficiency
What is Chronic visceral acid sphingomyelinase deficiency?
Chronic visceral acid sphingomyelinase deficiency (ASMD) — also known as Niemann-Pick disease type B, or non-neuronopathic Niemann-Pick disease — is a rare inherited condition caused by a shortage of an enzyme called acid sphingomyelinase. This enzyme normally breaks down a fatty substance called sphingomyelin inside cells. When it does not work properly, sphingomyelin builds up in organs throughout the body, especially the liver, spleen, and lungs. Unlike the more severe type A form, type B (chronic visceral ASMD) mainly affects the organs rather than the brain and nervous system, though some
How is Chronic visceral acid sphingomyelinase deficiency inherited?
Chronic visceral acid sphingomyelinase deficiency follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
Which specialists treat Chronic visceral acid sphingomyelinase deficiency?
1 specialists and care centers treating Chronic visceral acid sphingomyelinase deficiency are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.